Trailer shutoff valve



Oct. 3.4, 1947.

E. R. PRICE 2,429,197

TRAILER SHUT-OFF VALVE Filed Jan. 26, 1946 Patented Oct. 14, 1947 TRAILER sHU'roFF vALvE o Earl n. Page, south Bend, Ina., assigner tok Bendix Aviation Corporation, South.Bend, Ind., a corporation of Delaware Application January 26, 1946,' 'Serial No. 643,587

This invention relates to tractor-trailer controls, in which brakes are provided on both the tractor and the trailer and the entire braking system is capable of beingy put in to operation by a single control member.

In certain types ofearth-moving equipment, it is customary to use a tractor-trailer combination in which the controls are located on the tractor While the actual working equipment is provided on the trailer. Most of these tractortrailer combinations are heavy and Adiillcult to maneuver, and they are usually extremely hard to steer. I 1

It is proposed to ease the steering of such tractor-trailer combinations by utilizing selective application of the tractor brakes Vto assist the usual steering control. This means that, if the vehicle is to be turned to the left, the brake on the left wheel of the tractor is actuated,whi1e lthe brake on the right Wheel of the Atractor is prevented from operating, thereby permitting the right wheel to turn freely while the left wheel acts as a pivot. On the other hand, if the vehicle is to be turned toward the right, the brake on-the right wheel isvapplied but the left wheel brake is prevented from applying.v

Y If brakes are provided for the trailer, it is customary that the Voperation of these brakes Vbe synchronized with the operation of the tractor brakes. In -other words, the operator of the tractor, by manipulation of thefoot pedal or thelike, is able to cause operation of the trailer as well as the tractor brakes.

The primary object of the present invention is being used for steering purposes, while permit.

ting the trailer brakes to operate synchronously with the tractor brakes Whenever the. purpose is to slow or stop the tractor-trailer combination.

Stated another way, the object of the present invention is to provide a shut-oil valve for the trailer brakes which will normally connect said brakes to the usual control line, but which will automatically shut off the trailer-brakes Whenever the tractor brakes are being used for steering purposes.

Further objects and advantages of the present invention will become apparent during the course of the following description. In the drawings:

Figure 1 is a diagrammatic showing of the brake control system of a tractor-trailer vehicle combinatiomand Figure 2 is a sectional view of the trailer shut- OIT valve of Fig. 1. j

inder is continuously open to air at atmospheric pressure. A vacuuiir line 30 aconnects one port of relay valve `26-with the'vacuum reservoir 32 of the trailer; which is-in turn connected by means of a conduit 34 with the source of vacuum on the tractor. Thissource of vacuum maylcon-V sist of a vacuum'pump 36, and a vacuum voir 38 may be provided on the tractor. 'fr The right hand brake I2 of the tractor ls-cnnected by means of a hydraulic line 39l t'o a selector Lvalve`4ll and the left hand brake|4 of the resertractor is connected by means of the hydraulic li'ne 42 to the'selector valve 40. A conventional master cylinder 44 controlled by the usual pedal 46 is arranged to displace liquid through line 43 to cause application of the brakes. In the illustrated arrangement, a power device 50 is utilized to assist the manual effort. of the operator in building up hydraulic pressure at the brakes I2 and I4. The powerassistor 504s caused to operate by the pressure developed in line 48 and it in turn causes the displacement of liquid under pressure through line 52 to selector valve 40.

Operation' of selector valve 40 is under the con-- trol of v,the'steering apparatus of the tractor, the rod 54'having a gear 56 mounted thereon which meshes with a sector 58 controlled by turning lthe steering column 60. The arrangement of selector valve 40 is such that it causes one or the otherf the tractor brakes to be shutoff, i. e., disconnected from line 52, if the, steering column 60 is turned more than a predetermined amount vfrom central-or straight-ahead position. Thus, if pressure is developed in master cylinder 44 and consequently in powerdevice 50 at a time when one-of the brakes is cut off by selector valve'40. the brake pressure will assist in steering the vehicle because the tractor will tend to pivot on the wheel which is .being braked, i. e., the wheel which has not been cut oiT by selector valve 40.

The control valve which regulates operation of power device-50 under the influence of pressure developed in masterzcylinder 44, is shown in out.

pipej34. l

3 line at 62. A pipe 64 leading from this valve constitutes the control line for the trailer brakes, i. e., when in communication with line 28 it causes the trailer brakes to be applied whenever the tractor brakes are applied.

' In order to insure that the trailer brakes will not apply when thetractor brakes are'being used merely for assistance in `steering thevehicle, and

when it is not desired to retard thetractor-trailer I combination, I have provided a shutoff valve 68 ure 2. y I

Referring to Figure 2, it will be l"seen that' the casing 68 of shutoi valve B6 is provided with three ports associated with the operation ofthe trailer l relay valve, i. e., ports 10, 12 and 14 (the latter being shown by dotted line) Port 10 is connected to pipe B4, port 12 is connected to pipe 28, and port 14 is connectedto apipe liwhich leads to vacuum Reciprocable vwithinj casing 88 of the shutoff valve is a combined Vpiston and-plunger-valve `member' 18.1, The member 18 is provided withv a' pressure responsive piston head 80 at one end and a second pressure responsive piston head 82 at the other end, suitablesealing members 8g4-and 86 being provided at saidpiston heads. `Atthe left end moi the valve casing is a port 88 which connects with a-conduit 90 leading to hydraulic line42.

Y At theirightendof `the shutoil'valve is a port 92 which connects with .a conduit 94 leading tothe hydraulic line-38.'.V

Piston 18 ismnormally retained in its central position-by means of springs 9B and 88 which ordinarily retain perforated positioning members and |02 against Yshoulders |04V and |06 provided at opposite ends of the valve casing. Thus the' positioning members. |00 and |02 are normally held against the respective shoulders and Y the members 18 is. centralized. between them. y. However, the yieldability of springs 96 and98 permits the piston member 18 to move in either dl- Y rection ifa suiiicient differential develops be# Vtween .the pressures prevailing at oppositeY ends thereof. v

Between the end faces 00 and 82 of piston member 18 are threereduceddiametcr portions of the piston, namely portions |081, ||0and ||2.' The provision of lands ||4 and H6 thus provides annular chambers H8, |20 and |22. Chambers ||8 and 22 are permanently interconnected by means of a longitudinal passage |24 and lateral passages |26 andV |28 formed in the body of the piston member 18.

Operation of the trailer shutoff valve 66 is as follows.` In the position shown inFigure 2, an-

. nuiar chamber |20interconnects ports 10 and 12,

4 in steering, and the only tractor brake which is applied is the right hand brake, then hydraulic pressure will be built up at the right end of piston member 18 but not at vthe left end thereof, and therefore spring 96 will be compressed and piston member 18 will move toward the left. When memberl has moved a sulicient distance, port Vwill be closed. However, because port 12 is .wider than port 10, it will remain open and will l0` for controlling operation of the trailer vbrakes., A sectionalview of this valve is shown in Figcome into communication with chamber |22 and thence with port 14 and pipe 16. Therelay valve 26 will therefore communicate with the vacuum Y' source and it will remain in an inactive or released position; It has been mentioned above that pipe 64 is maintained under vacuum so long as the brakesof .the tractor and trailer are released. Therefore, connecting the relay valve 26 directly to the vacuum source, whenever it is desired to prevent the trailer brakes from operating. will in sure that said trailer brakes remain inactive. The

= reason for connecting the trailer relay valve to the :vacuum source after said relay valve has been cut off from line 64 is to prevent possible leakage in shutoi valve 66 from permitting a gradual application of the trailer brakes Where such application is-not-desired because the tractor brakes are being used for steering purposes only.

If the tractor brakes are to be used for steering Y and theleft-hand brake is to be applied while the right-hand brake is to be released, then hydraulic pressure will be developed at the left end of pis- Vton member 18 and not at the right end thereof,

and consequently saidpiston member will move toward theright. This movement will cause port trailer vehicle combination is being turned.

It will -be noted that the plugs |30 and |32 in lwhich the ports 88 and 92 are provided have extensions V|34 and |36 which limit the endwise movement of piston member 18, thereby preventing said member from moving far enough in either with the tractor brakes. This situation will exist when thetractor-trailer combination is moving straight ahead or is turning at an angleinsulcient to cause operation ofselector valve 40, In this circumstance, hydraulic pressure will be developed in both the right hand brake and the left direction to close port 12.

Bleedports |38 and |40 are provided at the top of shutoff valve 68 near opposite ends thereof, the usual bleed plugs |42 and |44 being inserted in the respective bleed ports.

Although a particular embodiment of my invention has been described, it will be understood by those skilled in the art that the object of the invention may be attained by the use of constructions different incertain respects from that disclosed without departing from the underlying principles of the invention. I therefore desire by the following claims to include Ywithin the scope of my invention all such variations and modifications by which substantially the results of my invention may be obtained through the use of substantially the same or equivalent means. 65

I claim:

l. A tractor-trailer braking system comprising Vbrakes on the trailenebrakes on the tractor, a

contol on the tractor for causing operation of both the tractor brakes and the trailer brakes, means for causing 'said control to apply the Ybrake on only one side of the tractor to assist in steering, and means for automatically disassociating Vthe trailer brakes from said control whenever said causing means is operative.

2. For use in a tractor-trailer braking system having a pneumatic power device for applying the trailer brakes, a control line for the trailer power device, a hydraulic master cylinder on the tractor, a left wheel brake on the tractor adapted to be applied by pressure developed in the master cylinder, a right wheel brake on the tractor also adapted to be applied by pressure developed in the master cylinder, and a selector adapted to cause the master cylinder pressure either to apply both tractor brakes or to apply only a selected one of them; a trailer brake shutoff valve comprising a casing having a port connected to the trailer power device, a second port connected to the control line, and a third port connected to a pressure source corresponding to the control line pressure when the brakes are released, and a piston reciprocable in the casing having one end subjected to a pressure corresponding to that in the wheel brake on one side of the tractor and the other end subjected to a pressure corresponding to that in the wheel brake on the other side of the tractor, said piston being so ported as to interconnect the first and second ports when in its central or neutral position, but being arranged when displaced in either direction from its central position to disconnect the rst port from the second port and connect it instead to the third port.

3. A control valve comprising a casing havingl 6 member reciprocable in said casing and having a head at each end acted on by the liquid entering the respective hydraulic port, and porting in said reciprocable member arranged to interconnect a certain two of the atmosphere ports when said member is in its central position, but to connect a given one of said two` ports to the third atmosphere port whenever said member moves in either direction from its central position.

4. A control valve comprising a casing having three atmosphere ports provided in the side walls thereof, and two hydraulic ports, one Vat each end,

a combined piston and plunger valve member reciprocable in said casing and having a head at each end acted on by the liquid entering the respective hydraulic port,` a positioning element at each end of the said reciprocable member for locating the same in its central or neutral position, a spring between each positioning ele EARL R. PRICE. 

